A US magistrate judge ­rejected Thursday an attempt by federal law enforcement to seize a Tewksbury motel ­because of drug activity that took place there.

“After careful consideration of the evidence, pleadings, and argument of counsel, this court concludes that the government has failed to meet its burden of establishing that the motel is subject to forfeiture,” US Magistrate Judge Judith Dein wrote in her ruling Thursday.

In September 2009, the government sought the forfeiture of the 56-room Motel Caswell, citing 15 drug-related incidents that occurred at the motel ­between 1994 and 2008. The owner, Russell H. Caswell, 69, lives next to the motel and purchased the property from his ­father in 1984, according to court documents.

Among the incidents cited by the government were the 1994 conviction of a motel occu­pant on charges of possession of a Class B substance with intent to distribute and the 1997 arrests of four heroin suppliers who delivered the drug to motel occupants.

“In none of the 15 incidents on which the government relied did Mr. Caswell or motel employees have knowledge that the guest was intending to use or distribute drugs or engage in unlawful activity at the time they checked in,” Dein wrote.

Caswell could not be reached for comment Thursday evening. A spokeswoman for the US attorney’s office in ­Boston would not comment. ­except to say that the office was still reviewing the ruling.

Prior to the 2009 forfeiture action, there had never been a threat of litigation against the motel, and law enforcement ­officials never advised Caswell about measures he could take to reduce drug crime at the ­motel, the judge wrote.

Dein also found that Caswell met his burden of proving that he was the “innocent owner” of the property, writing that ­Caswell “did not have actual knowledge of the forfeitable drug crimes before or while they were occurring, and there is no evidence that he should have known that they were likely to occur.”